NBC News Correspondent Kerry Sanders recently returned from Antarctica, where he chronicled the dramatic changes in the world's last wilderness. Below is his main report; you also can click on the map above for more dispatches from across the breathtaking seventh continent.

By Kerry Sanders, Correspondent, NBC News

ANTARCTIC PENINSULA — There are serious changes taking place here at the bottom of the world.

Increasingly, experts say, the ice is disappearing at a disturbing rate in the Antarctic Peninsula and that in turn impacts the future -- and perhaps the very existence — of at least half of the world’s 18 penguin species, who depend on ice and frigid waters that support krill, the penguin diet mainstay.

"When cheetahs or lions get hunted, or elephants decline, there’s a big uproar. And I think, because you see penguins in large numbers [in some places] people are ignoring the larger rate of their decline," said Oxford University penguinologist Tom Hart. "The general public doesn't realize the penguins are declining so fast."

But it’s not just the penguins we have to worry about, Hart says, it’s the health of the planet itself.

"The last wilderness on Earth is impacted by us now," he said, describing the region’s decline as a "grave indicator" of what’s to come.

Marine biologist Fabrice Genevois speaks with NBC's Kerry Sanders about Gentoo penguins and their extraordinary way of swimming which at times can appear as if they are "flying."

Life’s cycle disrupted for Antarctica’s penguinsIt’s the end of the breeding cycle for most penguins here as summer comes to a close. The Gentoos, Adelies and Chinstraps are nudging their newborns from the rocks of Antarctica’s peninsula toward the waters of the Southern Ocean.

Experts say about 50 percent of the eggs will produce a penguin chick that makes it to sea. And about half of those will survive the hungry predators below, as they plunge into the frigid waters for their first swim. Leopard seals are lurking -- and for the newborns, avoiding their mortal enemy is not easy. Many will die. Those that do survive are subject to climate change that is threatening their food supply.

Hart has spent nearly a decade studying the creatures that have captured the world’s imagination for centuries. Each year, for three to four months, he positions himself along the Antarctic coast to observe, measure and chart penguin colonies. Some colonies have been followed since polar explorer Sir Ernest Shackleton and his men headed here some 100 years ago.

Modern-day expeditions to Antarctica are a more pampered escape than the harrowing ordeals they once were, but a couple men remember the heroes of previous expeditions a little better than most. NBC's Kerry Sanders reports.

"When you look at all penguins they are largely in trouble," said Hart. "We're so concerned because we're seeing massive changes to their populations. They’re probably not going to go extinct anytime soon, but the environment is changing very fast.

Chinstraps populations seem to have declined up to 50 percent in the last 30 years," he added.

Hart, like most experts, is cautious to speak in absolutes because the harsh environment here makes it difficult to get a clear picture of what’s happening. Experts use time-lapse cameras and sit at computers, laboriously counting penguins one by one to compare colony sizes from year to year.

To keep track of the penguin population in the extreme conditions of Antarctica, scientists turn to time-lapse photography as an important tool for research. This video shows years of the animals' migration patterns.

Krill decline quickly as sea ice disappearsIce is the source of all life in Antarctica. It may seem at odds to think that ice gives life, but when you connect the dots, it’s a straight line to a penguin’s belly.

Algae live on top of the ice and underneath it too, providing a grazing ground for the krill that amass beneath -- the way a raccoon chooses to hide in a garbage can.

Krill mostly stay put under the frozen Southern Ocean. But as the ice sheet disappears due to climate change, that habitat shrinks and moves further south.

"The West Antarctic Peninsula has increased three degrees since 1951,” Hart said. "We’ve seen a large reduction in sea ice over the same period."

Although the climate has always undergone oscillations in temperature, Hart says the recent changes are happening much faster than normal.

NBC's Kerry Sanders takes a look at some of the unusual and fascinating wildlife that inhabits Earth's coldest continent.

Logically, less ice has resulted in less krill, say marine biologists. And since krill is the main diet for penguins, seals and whales, less food has in turn meant fewer births. That theory is widely accepted by scientists like French marine biologist Fabrice Genevois.

He says it’s mostly Americans, who have confused politics with science by questioning global climate change.

"We have all the information now, that's clear enough,” said Genevois. "There's no argument any more. You have to be either a liar or be crazy not to understand what we are doing to change the climate. We are responsible, that's for sure."

Add to that equation: Fishing. Less ice has opened areas to more fishing boats that in turn have targeted krill as a profitable catch.

There’s a 620,000 ton catch limit for krill in Antarctica, which is only about 1 percent of the total estimated mass in the region.

NBC's Kerry Sanders pays a visit to Antarctica, one of the world's last wilderness areas, to see the penguins that are being threatened by the increasingly rapid melting of the ice that dominates the landscape.

But it’s the location of the krill fisheries — all aggregated in the Antarctic Peninsula near the South Shetland Islands — that is the main cause of concern.

The boats increasingly drop their nets in the same waters where penguins search for food. The nets are not catching penguins indiscriminately but they are competing for the krill that the wildlife eats to survive.

Where do those captured krill end up? In part, they’re used as fish food at salmon farms, desirable because krill help color salmon “pink” which increases sales at the supermarket.

Canary in a coal mineThe entire population of Emperor penguins, Chinstraps and Adelies live in Antarctica — if the ice continues to retreat those species are at risk. Meanwhile, the potential for disease outbreaks increases.

"As regions of Antarctica warm it has much more potential as a petri dish," said Hart, citing disease from the north, in particular avian disease, as being a main concern.

The penguins, marine biologists say, are giving us a warning.

"We don't need to necessarily fear change," said marine biologist Maria Clauss, who works with tour company Quark Expeditions. But the penguin’s decline "will change the world as we know it," she said. "And we should not kid ourselves."